59606 - Numerical Investigation of Loss Development in a Low-Pressure Turbine Cascade With Unsteady Inflow and Varying Inlet Endwall Boundary Layer 

In modern jet engines, the trend to higher loaded airfoils in low-pressure turbines remains ongoing. The resulting high-pressure gradients in the blade passage lead to intensified secondary flows which induce a significant share of overall losses.

A numerical investigation of loss development is conducted in three cases of different inlet endwall boundary layer conditions, with and without periodically incoming bar wakes in the T106A low-pressure turbine cascade. The (U)RANS predictions are evaluated using experimental data measured under realistic flow conditions (Ma_2th = 0.59, Re_2th = 200 000). Overall, it is found that the numerical results show a good qualitative prediction of the measured flow phenomena, however, some the effects are exaggerated.

First, unsteady inflow conditions and varying inlet endwall boundary layer conditions are compared in terms of their effects on the secondary flows downstream of the bade passage by analyzing steady, time averaged, and time-resolved flow fields. The scope of the investigation is then extended into the axial loss development in the entire blade passage. For this purpose, the overall losses are separated into midspan losses i.e. profile losses and secondary losses. Similarities are found between the time-averaged effects of unsteady inflow conditions and changing the inlet endwall boundary layer conditions regarding the attenuation of the downstream secondary flow. However, their effects on the upstream loss development leading up to this point are entirely different. Further details on the flow phenomena leading to the observed effects on the loss development in different sections of the blade passage will be discussed in the full-length paper. Ultimately, the goal is to take a step forward in gaining a better understanding of the development of endwall flow in low-pressure turbine cascades and the associated loss generation mechanisms.